Known vehicle steering systems have included one apparatus for use in steering the front wheels of a vehicle and another apparatus for use in turning steerable rear wheels of a vehicle. Known devices for turning steerable rear wheels of a vehicle are disclosed in U.S. Pat. No. 6,945,350 and U.S. Published Patent Application No. 2007/0144818. Apparatus for use in turning steerable front wheels of a vehicle is disclosed in U.S. Published Patent Application No. 2007/0095598.
When a vehicle is proceeding straight ahead, it is desirable to have steerable rear wheels of the vehicle in an initial or straight ahead condition. Upon turning of the steerable front wheels of a vehicle, it may be desired to effect turning movement of steerable rear wheels of the vehicle. Upon movement of the steerable front wheels of the vehicle back to their initial or straight ahead condition, it may also be desired to have the steerable rear wheels of the vehicle return to their initial or straight ahead condition.